I'll take the last issue first.
SYNCING
Syncing will just compound other issues. Leave syncing in BookMacster off until we resolve the other two.
CHROMIUM EXPORTS NOT STICKING
Please try to export to Chromium with immediate, consecutive exports like this:
• Click in the menu: File > Export to only > Chromium.
• If asked about the Safe Limit,
Export Anyhow.
• After the export completes, immediately File > Export to only > Chromium again.
This time, there should be no Safe Limit warning, and the Status field at the bottom of the window, should indicate 0 changes (+0 Δ0 ↖0 ↕0 -0). Does that work?
FIREFOX LAUNCHING
You have two Firefox profiles, maybe more. One of them in your screenshot, the one that begins: default-14190XXX, is an new profile which Firefox creates after Firefox has been reset. I need to retest how this should work, but in the meantime, please straighten out those Firefox profiles. I like to use
Jonathan Griffin's Profile Manager app which you can
download from here. See how many Firefox profiles you have, remove unwanted profiles if any and, I suggest, rename them to remove the weird numbers. (That 14190XX… is the time from the Unix epoch that the profile was created.)